Environmental control of defensive reactions to footshock

Abstract

Footshock given immediately after rats are placed in a strange inescapable environment produces no diminution in movement. However. if a brief exploration period is allowed before shock. freezing is the dominant defensive behavior seen. Thus. the topographical similarity of postshock reactions to unconditioned defensive behaviors elicited by a cat also involves a similar flight-to-freezing shift when the subject is permitted prior familiarization with the inescapable threat situation. Blanchard, Fukunaga, and Blanchard (1976) have reported that a brief familiarization period in a novel, inescapable chamber changes the dominant defensive behavior of a rat to a cat in that chamber, from flight to freezing. In view of the similarity between cat-elicited defensive behaviors and reactions to conditioned threat stimuli (Blanchard & Blanchard, 1971), it seems likely that a similar shift might occur with familiarization of a chamber in which foot shock is given. Thus, in order to assess the generality of effects of familiarity with the inescapable test situation on defensive reactions to threat, th.e procedure employed in Blanchard, Fukunaga, and Blanchard (I 976) was repeated, using shock rather than a cat as the threat stimulus. METHOD SubjectsTwenty-four naive albino rats from 135 to 192 days of age were randomly· assigned to three groups of eight rats each. These rats Were from the colony maintained by the University of Hawaii Psychology Department. ApparatusA l1at-gray 50 x 50 x 15 em wooden box with a solid wood cover containing an 18 x 18 cm Plexiglas insert served as the test chamber. The chamber was placed on a grid 1100r consisting of 64-<:m stainless steel rods which were suspended over a Formica base divided by lines into four 25 x 25 cm areas.Shock was delivered to the grids by a Grason-Stadler E 1 064 shock source. A 60-W bulb suspended 20 em over the Plexiglas insert in the ceiling of the chamber provided illumination. A 65-<ib SPL speech noise from a Grason-Stadler noise generator was provided throughout the experiment. ProcedureThe three groups of the present experiment were identical to those of Blanchard, Fukunaga, and Blanchard (1976), except that shock instead of a cat was used as the threatening stimulus. The no-shock group was left in the apparatus for a 7-min period; the immediate-shock group ·was given a single 3-mA shock, 2 sec in duration, immediately upon placement in the test chamber; the delayed-shock group was left in the apparatus for Requests for reprints should be sent to Robert J. Blanchard, University of Hawaii, Department of Psychology, 2430 Campus Road, Honolulu, Hawaii 96822. 2 min, then briefly lifted and replaced at the same time that a shock of identical intensity and duration as that of the immediate-shock group was given. Both shock groups were observed for 5 min after shock, and measurements of movement times were made each minute that a rat was in the apparatus. Since shock always elicited jumping and running, and these movements persisted for brief periods after the shock t...

Potent attenuation of context fear by extinction training contiguous with acquisition

“…2A -D). Consistent with a variety of other studies demonstrating the immediate shock deficit (Blanchard et al 1976;Fanselow 1986Fanselow , 1990Kiernan and Cranney 1992;Westbrook et al 1994;Bevins and Ayres 1995), the shortest preshock interval (2 sec) produced very low levels of freezing in the context test regardless of the postshock duration ( Fig. 2A; F (1,15) ¼ 0.01).…”

Context representations, context functions, and the parahippocampal–hippocampal system

“…First, unlike an object, there is nothing arbitrary about shock or its biological significance. Consequently, shock activates a behavioral system (Bolles 1970;Blanchard et al 1976;Fanselow 1991) designed to defend and protect the animal from danger. Moreover, there is a known neural circuit in the amygdala complex that supports this behavioral system (LeDoux 1994(LeDoux , 1995Maren 2003;Phelps and LeDoux 2005;Davis 2006).…”

“…Sometime later the rat is returned to that context and tested several minutes for its fear of the ''conditioning context.'' The usual dependent variable is the time the rat spends freezing, a naturally occurring defensive response to threat (Blanchard et al 1976).…”

Activation of Hippocampal Nuclear Factor-κB by Retrieval Is Required for Memory Reconsolidation

“…Mice remained in the new context only 1 s before being shocked and then were immediately removed. Under these conditions, the association between this context and footshock is not established, a phenomenon known as immediate shock deficit (Blanchard et al, 1976;Fanselow, 1986Fanselow, , 1990Landeira-Fernandez et al, 2006). This procedure was repeated during 6 d. On the seventh day, animals received the shock in the training chamber and were killed 45 min later (Fig.…”